Brake rotors for some vehicles are manufactured by initially forming brake rotor preforms 10 (also sometimes referred to herein as “preforms”) that are subsequently machined to produce the brake rotors. The brake rotor preforms 10 (and, hence, the brake rotors) are formed from a plurality of segments 12 comprising carbon fiber precursor that are laid and abutted end-to-end about a central longitudinal axis 14 to form an annular spiral structure 16. The spiral structure 16 has a plurality of flights 18 (see FIG. 1 in which a single flight 18 is illustrated) similar to those of screw thread, but different from a screw thread in that each successive flight 18 lies longitudinally adjacent to and in contact with a previous flight 18 such that the flights 18 are in contact with one another in the longitudinal direction. Each flight 18 comprises multiple segments 12 with each segment 12 having a partial annular shape such that each segment 12 comprises a sector of an annulus. As more clearly seen in FIGS. 2 and 3, each segment 12 also has an inner radius, RI, an outer radius, RO, an included central angle, β, about longitudinal axis 14, a first end 20, and a second end 22. Referring back to FIG. 1, the spiral structure 16 also has a plurality of radially-extending butt joints 24, with each butt joint 24 being formed between abutting ends 20, 22 of respectively adjacent segments 12. The central angle, β, of each segment 12 is generally selected to determine the number of segments 12 per flight 18 of the spiral structure 16 and is selected so that the butt joints 24 between segments 12 of a flight 18 are not coplanar with the butt joints 24 between segments 12 of a longitudinally adjacent flight 18. The segments 12 of a particular flight 18 typically comprise carbon fiber precursor tow oriented in either a chordal direction (see FIG. 2) or in a radial direction (see FIGS. 3 and 4). Generally, the segments 12 of adjacent flights 18 do not include carbon fiber precursor tow oriented in the same direction in order to improve the mechanical and structural properties of the brake rotor preform 10.
The above described preform architecture has been successfully used for brake rotors employed in the aerospace industry where there are, typically, at least two rotors and three stators in a brake stack and axial compression of the stack is used to create and control friction to provide braking. More recently, preforms 10 having such architecture have been used in brake applications having a single carbon-carbon brake rotor disk 30 (also sometimes referred to herein as a “brake rotor 30”) machined from a preform 10 to have opposed front and back friction surfaces 32. Braking friction is generated by applying axial force (a force applied in the longitudinal direction of the brake rotor) on only the portions of the brake rotor's friction surfaces 32 which are present between two brake pads 34 (see FIG. 5 in which only one friction surface 32 and one brake pad 34 are visible) held by a caliper. Similar to the segments 12 of the brake rotor preform 10 from which the brake rotor 30 was machined, each brake pad 34 has a partial annular shape with a first end 36 and a second end 38. In such brake applications, the brake pads 34 often do not compress the friction surfaces 32 of the brake rotor 30 uniformly at all times. When compressed with the brake rotor 30 turning between brake pads 34, the compression is sometimes uneven in the axial direction, causing a shear force within the carbon-carbon brake rotor 30. When the butt joints 24 between adjacent segments 12 of the flights 18 of the brake rotor preform 10 (and, hence, of the brake rotor 30) rotate about central longitudinal axis 14 (for example, in the rotational direction 40) past an end 36, 38 of the brake pad 34, the butt joints 24 are radially aligned momentarily at different times in a radially extending plane 42, 44 with either the first end 36 (see FIG. 6) or second end 38 (see FIG. 7) of the brake pad 34 and the shear force causes the carbon-carbon composite of the brake rotor preform 10 (and, hence, of the brake rotor 30) to fracture at or near the butt joints 24 between adjacent segments 12. These fractures then typically propagate through the carbon-carbon composite and cause the entire brake rotor 30 to fail.
There is, therefore, a need in the industry for brake rotor preforms, brake rotors, and/or brake pads having configurations and architectures that solve these and other problems, deficiencies, and shortcomings of the present configurations and architectures.